<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>等高布局</title>
	<style>
		.box{
			border-left: 300px solid #222;
		}

		.left {
			width: 300px;
			margin-left: -300px;
			color: white;
		}
		.left > span {
			float: left;
		}
	</style>
</head>
<body>

<div class="box">
	<nav class="left">
		<span>导航1</span>
	</nav>
	<section>
		<div class="module"><span>模块1</span></div>
	</section>
</div>
<script>
	function addNav() {
		document.getElementsByClassName('box')
	}
</script>
</body>
</html>